At present, the liquid crystal compounds are widely applied in various types of displays, electro-optical devices, sensors and the like, and a large number of liquid crystal compounds have been used in display area, wherein the nematic liquid crystal is most widely used. Nematic liquid crystals have been used in passive TN (twisted nematic), STN matrix display and TFT active matrix system.
The liquid crystal mixtures used in super twisted nematic (STN) mode, often require a large multiplex, a low threshold voltage, and a broad nematic phase range. It is desirable to further improve the properties of liquid crystal monomer used in the mixture for STN mode, especially widening the application range.
Although thin-film transistor technology (TFT-LCD) is maturing, it is still desirable, among other things, to improve the response speed, reduce the drive voltage to decrease the power consumption. It is well-known that liquid crystal materials play an important role to improve the characteristics of the liquid crystal display, as the liquid crystal material, needs to have good chemical and thermal stability and stability of the electric field and electromagnetic radiation. Liquid crystal material for thin-film transistor technology (TFT-LCD) not only requires the stability to heat, UV light, electric field and electromagnetic radiation, but also requires a wide temperature range of a nematic phase, an appropriate optical anisotropy, high resistance, a high voltage holding ratio, and low vapor pressure.
A low rotational viscosity γ1 (even at low temperature), a high dielectric anisotropy (Δ∈) of the liquid crystal mixture has an important significance to improve performance of liquid crystal displays. Therefore, the development of liquid crystal monomer having appropriate physical and chemical properties is the top priority in the future research.